This invention relates to the field of radio wave communication, and more specifically to radio wave antennas that have multiple resonant frequencies and are utilized, for example, in a wireless communications system.
Antennas having more than one radiating/receiving element (hereinafter radiating element) are known.
U.S. Pat. No. 5,771,023 (incorporated herein by reference) describes an antenna wherein a first helical antenna is carried by a hollow insulating sleeve, and wherein an insulating assembly that includes a straight-wire antenna and a second helical antenna may be moved to either an extended or a retracted position within the insulating sleeve. When this antenna is in an extended position, the straight-wire antenna is located above the insulating sleeve, and the straight-wire antenna forms a main antenna function. When this antenna is in a retracted position, the straight-wire antenna is essentially inactive, and the two helical antenna are active.
U.S. Pat. No. 6,249,257 (incorporated herein by reference) provides a switched, dual-band, retractable antenna having a hollow and stationary assembly that includes an inner and an outer helical radiator, and having an elongated monofilar radiator that is movable within this hollow assembly. When the monofilar radiator is extended, the monofilar radiator is connected to an associated telephone, as the two helical radiators are disconnected from the telephone. When the monofilar radiator is retracted, the two helical radiators are connected to the telephone, as the monofilar radiator is disconnected from the telephone.
U.S. Pat. No. 4,772,895 (incorporated herein by reference) provides an antenna wherein a first relatively long helical resonator has one end connected to a feed conductor, this same end of the first helical resonator being surrounded by a relatively short dielectric spacer. A second relatively short helical resonator surrounds the dielectric space, and a corresponding end of this second helical resonator is connected to ground. The dielectric spaced is constructed such that the grounded second helical resonator is tightly capacitive coupled or inductive coupled to the first helical resonator.
U.S. Pat. No. 6,300,913 (incorporated herein by reference) provides an antenna wherein a first flat or non-wire helical resonator is carried on the outside of a hollow housing, and wherein a second flat or non-wire helical resonator is carried by a member that is inserted into the hollow housing.
U.S. Pat. No. 6,127,979 (incorporated herein by reference) provides an assembly having a straight-wire whip antenna that is located within a helical antenna, wherein the whip antenna and the helical antenna are coupled to a single feedpoint, wherein a single matching network provides matching for both the whip antenna and the helix antenna, and wherein the antenna assembly can be reduced in size by attaching a disk to a top of the whip antenna.
Other examples of non-telescoping or stubby antennas for use within wireless communication devices such as cellular telephones include U.S. Pat. No. 6,133,885 and 6,275,198 (incorporated herein by reference.
This invention provides a non-telescoping antenna, also known as a stubby antenna. A non-limiting example of the utility of an antenna in accordance with the invention is for use as the transmitting/receiving antenna of a multi-band wireless communication device.
More specifically, the present invention provides a small-profile (about 10 to about 15 mm long) stubby antenna having (1) a relatively large diameter element, consisting of a metal element or a meander pattern wire that forms the antenna""s low-frequency-band radiating element, and (2) a centrally-located and smaller diameter coiled or bent metal wire whose top end is electrically connected to a metal disk that is located at the top of the stubby antenna, this small diameter coiled/bent wire and its disk forming the antenna""s high-frequency-band radiating element.
While the axis of this small diameter coiled or bent wire extends perpendicular to the plane of the metal disk, this construction and arrangement is not to be taken as a limitation on the spirit and scope of the invention.
In non-limiting embodiments of the invention the bottom ends of the two wire coils were mechanically supported by, and electrically connected to, a metal snap-in connector or a metal screw-in connector that was located at the base of the antenna, this construction and arrangement being adapted for use in mechanically and electrically coupling the antenna to a wireless communication device.
In non-limiting embodiments of the invention the two above-mentioned wire coils were formed of a silver-plated beryllium copper wire having a diameter of about 0.41 mm.
Within the spirit and scope of this invention, the above-described small diameter center wire coil can be formed by the three-dimensional series-connection of a number of spiral wire portions, or by the three-dimensional series-connection or the two-dimensional series-connection (i.e. in-plane connection) of a number of semicircular wire portions, or by the three-dimensional series-connection or by the two-dimensional series-connection of a number of triangular or zig-zag wire portions.
It is also within the spirit and scope of this invention to form the antenna""s top located metal disk, the antenna""s small diameter coiled or bent wire coil, and the antenna""s bottom-located connector as a single structural element.
It is also within the spirit and scope of this invention to form the large diameter coil element from a meander pattern, such as a flexible and metallized dielectric film, a stamped metal sheet, or a metal plated plastic.
The presence of the above-described coils or bends in the antenna""s small diameter center wire provides additional physical length to this center wire, thus providing better high band performance, while minimizing the physical length of the antenna. The antenna""s toplocated metal disk provides a specific absorption rate (SAR) improvement by moving the high current point of the antenna further away from head of a person using a cellular telephone that includes the antenna of the present invention.
Antennas in accordance with the invention include an exterior cup-shaped sheath that is formed of a dielectric material, for example a synthetic thermoplastic resin such as polycarbonate. This sheath either snaps onto, screws onto, or is adhesive-attached onto a similar plastic member that is associated with and supports the above-mentioned bottom-located metal connector. This exterior sheath can also be molded directly onto the metal snap-on or screw-in connector that is located at the base of the antenna.
Within the spirit and scope of this invention the antenna""s bottom-located plastic base and metal connector may included a snap-in coupling for physically and electrically mounting the antenna to an associated wireless communication device, or a screw-in coupling for physically and electrically mounting the antenna to an associated wireless communication device.